In the art of Coriolis mass flow rate meters it is well known that a vibrating flow conduit carrying mass flow causes Coriolis forces which deflect the flow conduit away from its normal vibration path proportionally related to mass flow rate. These deflections or their effects can then be measured as an accurate indication of mass flow rate.
This effect was first made commercially successful by Micro Motion Inc. of Boulder, Colo. Early designs employed a single vibrating U-shaped flow conduit which was cantilever mounted from a base. With nothing to counter-balance the vibration of the flow conduit, the design was highly sensitive to mounting conditions and so was redesigned to employ another mounted vibrating arrangement which acted as a counter-balance for the flow conduit similar to that disclosed in their U.S. Pat. Nos. Re. 31,450 and 4,422,338 to Smith. Problems occurred however since changes in the specific gravity of the process-fluid were not matched by changes on the counter-balance, an unbalanced condition could result causing errors. Significant improvement was later made by replacing the counter-balance arrangement by another U-shaped flow conduit identical to the first and splitting the flow into parallel paths, flowing through both conduits simultaneously. This parallel path Coriolis mass flow rate meter (U.S. Pat. No. 4,491,025 to Smith et al) solves this balance problem and has thus become the premier method of mass flow measurement in industry today.
Many other flow conduit geometries have been invented which offer various performance enhancements or alternatives. Examples of different flow conduit geometries are the dual S-tubes of U.S. Pat. Nos. 4,798,091 and 4,776,220 to Lew, the omega shaped tubes of U.S. Pat. No. 4,852,410 to Corwon et al, the B-shapes tubes of U.S. Pat. No. 4,891,991 to Mattar et al, the helically wound flow conduits of U.S. Pat. No. 4,756,198 to Levien, figure-8 shaped flow conduits of U.S. Pat. No. 4,716,771 to Kane, the dual straight tubes of U.S. Pat. No. 4,680,974 to Simonsen et al, and others. All of these geometries employ the basic concept of two parallel flow conduits vibrating in opposition to one another to create a balanced resonant vibrating system.
Although the parallel path Coriolis mass flow rate meter has been a tremendous commercial success, several problems remain. Most of these problems are a consequence of using flow splitters and two parallel flow conduits in order to maintain a balanced resonant system. In addition, most designs employ flow conduits that are curved into various shapes as previously described to enhance the sensitivity of the device to mass flow rate. These two common design features cause a number of problems which preclude the use of Coriolis technology in many applications that would benefit from its use.
Among the problems caused by the flow splitters and curved flow conduits are; (1) Excessive fluid pressure-drop caused by turbulence and drag forces as the fluid passes through the flow splitters and curves of the device. (2) Difficulty in lining or plating the inner surface of geometries having flow splitters and curved flow conduits, with corrosive resistant materials. (3) Inability to meet food and pharmaceutical industry sanitary requirements such as polished surface finish, non-plugable, self-draining, and visually inspectable. (4) Difficulty in designing a case to surround dual curved flow conduits which can contain high rated pressures. (5) Difficulty in designing flow meters for 6" diameter and larger pipelines. (6) Difficulty in reducing the cost of current designs due to the added value of flow splitters, dual flow conduits and curved flow conduit fabrication.
It is therefore recognized that a Coriolis mass flow rate meter employing a single straight flow conduit would be a tremendous advancement in the art. It is the object of the present invention therefore to disclose a means whereby a Coriolis mass flow rate meter can be created using a single straight flow conduit thereby eliminating the problems caused by flow splitters, dual flow paths and curved conduits while retaining the current advantages of balance and symmetry.